1. Field of the Invention
The present invention relates to a liquid discharging head in which desired liquid is discharged by growth of a bubble generated in liquid by applying thermal energy to the liquid, a head cartridge using such a liquid discharging head, and a liquid discharging apparatus having such a liquid discharging head.
The present invention is applicable to printers for effecting the recording on a recording medium such as a paper sheet, a thread sheet, a fiber sheet, a cloth, a leather sheet, a metal sheet, a plastic sheet, glass, wood, ceramic sheet and the like, copying machines, facsimiles having a communication system, word processors having a printer portion, and to industrial recording apparatuses compositely combined to various processing devices.
Incidentally, in this specification and claims, a term xe2x80x9crecordingxe2x80x9d means not only application of a significant image such as a character or a figure onto a recording medium but also application of a meaningless image such as a pattern onto a recording medium.
2. Related Background Art
There has been proposed an ink jet recording method, i.e., a bubble jet recording method in which change in state of ink including abrupt change in volume of ink (generation of a bubble) is caused by applying thermal energy to the ink and the ink is discharged from a discharge opening by an acting force due to such change in the ink state, thereby forming an image on a recording medium by adhering the ink to the recording medium. As disclosed in U.S. Pat. No. 4,723,129, a liquid discharging head used in such a bubble jet recording method includes discharge openings for discharging ink, ink passages communicated with the discharge openings, and heat generating elements (electro/thermal converters) disposed in the ink passages and acting as energy generating means for generating energy for discharging the ink.
FIG. 33 schematically shows a construction of a conventional liquid discharging head. Now, an arrangement and an assembling method of the conventional liquid discharging head will be briefly explained with reference to FIG. 33.
A liquid discharging head 200 comprises a heater board (element substrate) 101 on which a plurality of heaters (heat generating resistance elements) for applying thermal energy to ink are disposed, a grooved top plate 150 having a plurality of grooves constituting nozzles and a common liquid chamber communicated with the grooves, and a holding spring 178. The liquid discharging head 200 includes a chip tank 180 acting as a liquid supply member for the head 200 when connected to an ink tank 190, and a base plate 170 as a substrate having a circuit board 171. The liquid discharging head is assembled with the ink tank 190 to form a head cartridge.
In order to assemble these elements, after the heater board 101 is adhered to the base plate 170, the top plate 150 is temporarily adhered to the heater board 101 with the heaters aligned with the nozzle grooves. Thereafter, in a condition that the top plate is fixed under pressure with the heater board 101 by a press spring, the top plate and the heater board are heat-welded to the base plate 170, together with the chip tank 180. Lastly, the chip tank 180 is connected to the ink tank 190 by fitting the base plate 170 onto positioning pins 194, 195 of the ink tank 190 and heat-welding the base plate to the ink tank.
According to the ink jet recording method using such a liquid discharging head, a high quality image can be recorded at a high speed with low noise.
Further, in the head performing such a recording method, since the discharge openings for discharging the ink can be arranged with high density, not only an image having high resolving power but also a color image can easily be recorded with a compact structure. Thus, the bubble jet recording method has recently been used in various office equipments such as printers, copying machines, facsimiles and the like, as well as industrial systems such as print devices.
However, when the conventional liquid discharging head as shown in FIG. 33 is assembled, since the number of parts is great and the assembling processes are complicated, the liquid discharging head cannot be manufactured cheaply. Accordingly, the inventors aims to provide a liquid discharging head having a structure which can be assembled and manufactured easily and cheaply.
First of all, a liquid discharging liquid passage structure and a liquid discharging principle applied to a liquid discharging head of the present invention will be explained with reference to FIGS. 1A, 1B, 1C, 1D, 2, 3, 4, 5, 6, 7, 8A and 8B.
FIGS. 1A to 1D are schematic sectional views of a liquid discharging head taken along a liquid passage and showing liquid discharging steps, and FIG. 2 is a partial sectional perspective view of the liquid discharging head.
The liquid discharging head according to the illustrated embodiment includes an element substrate 1 on which a heat generating element 2 (rectangular heat generating resistance member having a dimension of 40 xcexcmxc3x97105 xcexcm, in FIG. 2) for acting thermal energy on liquid (as discharge energy generating element for generating energy for discharging the liquid) is arranged, and a liquid passage 10 is formed above the element substrate 1 in correspondence to the heat generating element 2. The liquid passage 10 communicates with a discharge opening 18 and also communicates with a common liquid chamber 13 for supplying the liquid to a plurality of liquid passages 10, and receives the liquid corresponding to the discharged liquid from the common liquid chamber 13.
Within the liquid passage 10, above the element substrate 1, a movable member 31 formed from material having elasticity such as metal is disposed in a cantilever fashion in a confronting relation to the heat generating element 2. One end of the movable member 31 is secured to bases (support member) 34 formed by patterning photosensitive resin on walls of the liquid passage 10 and on the element substrate 1. As a result, the movable member 31 is held in such a manner that the movable member can be displaced around a fulcrum (support portion) 33.
The movable member 31 has the fulcrum (support portion; fixed end) 33 positioned at an upstream side of large flow of liquid flowing from the common liquid chamber 13 through the movable member 31 to the discharge opening 18 and a free end (free end portion) 32 disposed at a downstream side of the fulcrum 33, and is disposed in a confronting relation to the heat generating element 2 to cover the heat generating element 2 and is spaced apart from the heat generating element 5 upwardly by about 15 xcexcm. A bubble generating area is defined between the heat generating element and the movable member. Incidentally, kinds, configurations and dispositions of the heat generating element 2 and the movable member 31 are not limited to the above-mentioned ones, but, the heat generating element and the movable member may be configured and disposed to control growth of a bubble and transmission of bubble pressure, which will be described later. In the present invention, since the free end 32 has an adequate width, growing power of the bubble can easily be directed toward the discharge opening 18. Incidentally, for the explanation of a liquid flow which will be described later, the liquid passage 10 is explained to have a first liquid passage 14 (at one side of the movable member 31) directly communicated with the discharge opening 18 and a second liquid passage 16 (at the other side of the movable member) including a bubble generating area 11 and a liquid supply passage 12.
Heat is applied to the liquid in the bubble generating area 11 between the movable member 31 and the heat generating element 2 by heating the heat generating element 2, and a bubble is formed in the liquid by a film-boiling phenomenon as disclosed in U.S. Pat. 4,723,129. Pressure caused by the formation of the bubble, and the bubble act on the movable member preferentially to displace the movable member 31 around the fulcrum 33 to be greatly opened toward the discharge opening, as shown in FIGS. 1B, 1C and 2. By the displacement or a displaced condition of the movable member 31, a transmitting direction of the pressure caused by the formation of the bubble and a growing direction of the bubble itself are oriented toward the discharge opening. In this case, since the free end 32 has the adequate width, the growing power of the bubble can easily be directed toward the discharge opening 18.
Now, one of fundamental discharging principles of the present invention will be described. The most important principle of the present invention is to displace or shift the movable member (disposed in a confronting relation to the bubble) from a first position (normal condition) to a second position (displaced condition) by the pressure of the bubble or the bubble itself, so that the pressure caused by the formation of the bubble and the bubble itself are oriented to a downstream side in which the discharge opening 18 is disposed, by the displaced movable member 31.
This principle will be fully explained while comparing FIG. 3 (schematically showing a structure of a conventional liquid passage not having the movable member) and FIG. 4 (showing the present invention). Incidentally, here, the pressure transmitting direction toward the discharge opening is shown by the arrows VA and a pressure transmitting direction toward the upstream side is shown by the arrows VB.
In the conventional head as shown in FIG. 3, there is no means for regulating a transmitting direction of the pressure caused by formation of a bubble 40. Thus, the pressure of the bubble 40 is transmitted toward various directions as shown by the arrows V1-V8 perpendicular to a surface of the bubble. Among them, the pressure transmitting directions V1-V4 have components directing toward the direction VA which is most effective to the liquid discharging, and the pressure transmitting directions V1-V4 are positioned on a left half of the bubble near the discharge opening and contribute to the liquid discharging efficiency, liquid discharging force and liquid discharging speed. Further, since the pressure transmitting direction V1 is directed to the discharging direction VA, it is most effective; whereas, the pressure transmitting direction V4 has smallest component directing toward the discharging direction VA.
To the contrary, in the present invention shown in FIG. 4, the pressure transmitting directions V1-V4 which are directed to various directions in FIG. 3 are oriented toward the downstream side (i.e., toward the discharge opening) by the movable member 31 (i.e., various pressure transmitting directions is converted to the downstream direction VA), with the result that the pressure of the bubble 40 contributes to the liquid discharging directly and effectively. Similar to the pressure transmitting directions V1-V4, the growing direction of the bubble is directed toward the downstream side, with the result that the bubble is grown more greatly at the downstream side than at the upstream side. By controlling the growing direction of the bubble itself and the pressure transmitting direction of the bubble by means of the movable member, the discharging efficiency, discharging force and discharging speed can be improved.
Next, a discharging operation of the liquid discharging head according to the illustrated embodiment will be fully described with reference to FIGS. 1A to 1D.
FIG. 1A shows a condition before energy such as electrical energy is applied to the heat generating element 2, i.e., before heat is generated from the heat generating element 2. It is important that the movable member 31 is disposed in a confronting relation to at least a downstream portion of the bubble which will be formed by the heat from the heat generating element 2. That is to say, the movable member 31 extends up to at least a position downstream of a center 3 of an area of the heat generating element in the liquid passage (i.e., downstream of a line passing through the center 3 of the area of the heat generating element and extending perpendicular to the length of the liquid passage) so that the downstream portion of the bubble acts on the movable member.
FIG. 1B shows a condition that the heat generating element 2 is heated by applying the electrical energy to the heat generating element 2 and the bubble is formed by the film-boiling caused by heating a portion of the liquid contained in the bubble generating area 11 by utilizing the heat from the heat generating element.
In this case, the movable member 31 is displaced or shifted by the pressure caused by the formation of the bubble 40 from the first position to the second position to direct the pressure transmitting direction of the bubble 40 toward the discharge opening. Here, it is important that, as mentioned above, the free end 32 of the movable member 31 is disposed at the downstream side and the fulcrum 33 is disposed at the upstream side (near the common liquid chamber) and at least a portion of the movable member is faced to the downstream portion of the heat generating element (i.e., downstream portion of the bubble).
FIG. 1C shows a condition that the bubble 40 is further growing and the movable member 31 is further displaced by the pressure caused by the growth of the bubble 40. The generated bubble is grown more greatly at the downstream side than at the upstream side, and the bubble is greatly grown to exceed the first position (dotted line) of the movable member. As mentioned above, since the movable member 31 is gradually displaced as the bubble 40 is growing, the pressure transmitting direction of the bubble 40 is regulated to a direction toward which the pressure transmitting direction is apt to be oriented or the volume of the bubble is apt to be shifted (i.e., to the free end), with the result that the growing direction of the bubble is uniformly oriented toward the discharge opening 18, thereby increasing the discharging efficiency. When the bubble and the bubble pressure are oriented toward the discharge opening, the movable member does almost not regulate such orientation, with the result that the transmitting direction of the pressure and the growing direction of the bubble can be controlled efficiently in accordance with the magnitude of the pressure transmitted. Further, since the free end 32 has the adequate width, the growing power of the bubble can easily be directed toward the discharge opening 18.
FIG. 1D shows a condition that, after the film-boiling, the bubble 40 is contracted and disappeared due to the reduction of pressure in the bubble.
The movable member 31 which was displaced to the second position is returned to the initial (first position) shown in FIG. 1A by negative pressure due to contraction of the bubble and the elastic returning force of the movable member itself. Further, when the bubble is disappeared, in order to compensate an amount corresponding to the contracted volume of the bubble at the bubble generating area 11 and to compensate an amount corresponding to the discharged liquid, the liquid flows from the upstream side B (i.e., from the common liquid chamber) as flows VDD1, VD2 and from the discharge opening side as a flow VC.
While the operation of the movable member and the liquid discharging operation due to the generation of the bubble were explained, now, re-fill of the liquid in the liquid discharging head of the present invention will be fully explained.
After the condition shown in FIG. 1C, when the bubble 40 having the maximum volume is being disappeared, an amount of the liquid corresponding to the reduced volume of the bubble flows into the bubble generating area from the discharge opening 18 side of the first liquid passage 14 and from the common liquid chamber 13 side of the second liquid passage 16. In the conventional liquid passage structure not having movable members 31, an amount of the liquid flowing into the bubble disappearing position from the discharge opening side and an amount of the liquid flowing into the bubble disappearing position from the common liquid chamber depend upon flow resistance between the discharge opening and the bubble generating area and flow resistance between the common liquid chamber and the bubble generating area (i.e., depend upon resistance of the liquid passages and inertia of liquid).
Thus, when the flow resistance between the discharge opening and the bubble generating area is smaller, a relatively large amount of liquid flows into the bubble disappearing position from the discharge opening side to increase a retard amount of meniscus. Particularly, as the liquid discharging efficiency is increased by reducing the flow resistance between the discharge opening and the bubble generating area, the retard amount of the meniscus M during the disappearance of the bubble is increased accordingly, thereby increasing the re-fill time, and, thus, preventing the high speed recording.
To the contrary, in the illustrated embodiment, because of the provision of the movable member 31, when it is assumed that an upper volume portion of a volume W of the bubble above the first position of the movable member is W1 and a lower volume portion of the bubble below the first position is W2, at the time when the movable member is returned to its initial position during the disappearance of the bubble, the retard movement of the meniscus is stopped. Thereafter, the liquid corresponding to the residual volume portion W2 is mainly sullied from the flow VD2 in the second liquid passage 16. Accordingly, although the retard amount of the meniscus corresponded to about a half of the bubble volume W in the conventional techniques, in the illustrated embodiment of the present invention, the retard amount of the meniscus can be suppressed to about a half of the volume portion W1, smaller than that in the conventional techniques.
Further, since the supply of the liquid corresponding to the volume portion W2 can be forcibly effected by utilizing the negative pressure (generated due to the disappearance of the bubble) mainly from the upstream second liquid passage (flow VD2) along a surface of the movable member 31 facing to the heat generating element, the re-fill time can be shortened.
When the re-fill is effected by utilizing the negative pressure during the disappearance of the bubble in the conventional head, the fluctuation of the meniscus becomes great to cause the deterioration of the image quality. To the contrary, in the high speed re-fill according to the illustrated embodiment, since the flowing of the liquid in the first liquid passage 14 near the discharge opening into the bubble generating area 11 near the discharge opening is suppressed by the movable member, the fluctuation of the meniscus M can be minimized.
In this way, according to the present invention, since the high speed re-fill is achieved by the forcible re-fill of the liquid into the bubble generating area from the liquid supply passage 12 of the second liquid passage 16 and suppression of the retard or fluctuation of the meniscus, the stable liquid discharging and high speed repeat discharging can be realized, and, when applied to the recording field, the high quality image and high speed recording can be realized.
In the arrangement according to the present invention, there is also provided the following effective function. That is to say, the transmission of the pressure caused by the formation of the bubble to the upstream side (back-wave) can be suppressed. The pressure of the bubble portion (near the common liquid chamber 13 (upstream side)) of the bubble generated on the heat generating element 2 tends to push the liquid back to the upstream side (to cause the back-wave). The back-wave creates upstream pressure, upstream movement of the liquid and an inertia force due to the liquid movement, which resist the re-fill of the liquid into the liquid passage, thereby affecting a bad influence upon the high speed recording. In the present invention, since such upstream pressure, upstream liquid movement and inertia force can be suppressed by the movable member 31, the re-fill ability can be further improved.
Next, a further characteristic construction and advantage therefor in the illustrated embodiment will be described.
The second liquid passage 16 according to the illustrated embodiment has the liquid supply passage 12 having an inner wall flatly contiguous to (i.e., flush with) the heat generating element 2 at the upstream side of the heat generating element 2. In such a case, the supply of the liquid to the bubble generating area 11 and the surface of the heat generating element 2 is effected along the surface of the movable member 31 facing to the bubble generating area 11 (as flow VDD2). Thus, stagnation of liquid on the heat generating element 2 is prevented, with the result that gas included in the liquid and the residual bubble can easily be removed and excessive accumulation of heat in the liquid can be avoided. Accordingly, more stable formation of bubble can be repeated at a high speed. Incidentally, in the illustrated embodiment, while an example that the liquid supply passage 12 has a substantially flat inner wall was explained, the inner wall of the liquid supply passage is not limited to such an example, but may have a gentle slope or other shape smoothly contiguous to the surface of the heat generating element to prevent the stagnation of liquid on the heat generating element and disturbance of the supplied liquid.
Further, in some cases, the supply of the liquid to the bubble generating area is effected through the side (slit 35) of the movable member 31. However, in order to direct the bubble pressure toward the discharge opening more effectively, as shown in FIG. 1, a large movable member may be used to cover the entire bubble generating area (entire surface of the heat generating element). In this case, when the flow resistance between the bubble generating area 11 and an area near the discharge opening in the first liquid passage 14 is great, by returning the movable member 31 to its first position, the flow of the liquid from VD1 toward the bubble generating area 11 is prevented. However, in the illustrated embodiment, since there is the flow VD1 for supplying the liquid to the bubble generating area, the liquid supplying ability is enhanced, so that, even when the structure in which the bubble generating area 11 is covered by the movable member 31 to improve the liquid discharging efficiency is used, the liquid supplying ability is not so worsened.
By the way, regarding the positions of the free end 32 and the fulcrum 33 of the movable member 31, for example, as shown in FIG. 5, the free end is disposed at a downstream side of the fulcrum. With this arrangement, when the bubble is being formed, the pressure transmitting direction and the growing direction of the bubble can be oriented or directed toward the discharge opening 18 effectively. Further, this positional relation not only contributes to the improvement of the discharging efficiency or ability but also reduces flow resistance of the liquid flowing through the liquid passage 10 during the supply of liquid, thereby achieving the high speed re-fill. The reason is that, as shown in FIG. 5, when the meniscus M retarded due to the liquid discharging is restored toward the discharge opening 18 by a capillary phenomenon and/or when the liquid is supplied to compensate the disappeared bubble, the free end and the fulcrum 33 are arranged not to resist against the liquid flows S1, S2, S3 flowing in the liquid passage 10 (including the first and second liquid passages 14, 16).
Further, in FIG. 1, as mentioned above, the free end 32 of the movable member 31 extends up to the position downstream of the center 3 of the area of the heat generating element 2 (i.e., downstream of the line passing through the center of the area of the heat generating element and extending perpendicular to the length of the liquid passage 10). Thus, the pressure and the downstream portion of the bubble 40 which are generated at the downstream side of the center 3 of the area of the heat generating element and greatly contribute to the liquid discharging are supported by the movable member 31, with the result that the pressure and the bubble can be directed toward the discharge opening, thereby improving the discharging efficiency and discharging force.
In addition, by utilizing the upstream portion of the bubble, various advantages can be achieved. Further, in the illustrated embodiment, the momentary mechanical displacement of the free end of the movable member 31 also contributes to the improvement of the liquid discharging.
FIG. 6 is a schematic sectional view of a liquid discharging head according to another embodiment of the present invention, taken along a liquid passage, and FIG. 7 is a partial fragmental perspective view of the liquid discharging head of FIG. 6. In this embodiment, although the main liquid discharging principle is the same as the first embodiment, the first liquid passage 14 and the second liquid passage 16 are isolated by a separation wall 30 having movable member 31 as will be described later so that liquid (bubble liquid) in which a bubble is formed by applying heat to the liquid is separated from liquid (discharge liquid) which is mainly to be discharged.
In FIGS. 6 and 7, a liquid discharging head according to this embodiment includes an element substrate 1 on which a heat generating element 2 for applying thermal energy for forming a bubble in the liquid is arranged, a second liquid passage 16 for the bubble liquid disposed on the element substrate 1, and a first liquid passage 14 for the discharge liquid directly communicated with the discharge opening 18 and disposed above the second liquid passage.
Regarding a structure of the first liquid passage 14 from an upstream side to a downstream side, as shown, a height of the first liquid passage is gradually increased with respect to the movable member 31 toward the discharge opening. In other words, flow resistance is selected so that the free end 32 of the movable member 31 can easily be displaced with respect to the fulcrum 33 in the first liquid passage 14.
An upstream side portion of the first liquid passage 14 is communicated with a first common liquid chamber 15 for supplying the discharge liquid to the plurality of first liquid passages 14, and an upstream side portion of the second liquid passage 16 is communicated with a second common liquid chamber 17 for supplying the bubble liquid to the plurality of second liquid passages 16.
However, when the same liquid is used both as the bubble liquid and as the discharge liquid, a single common liquid chamber may be used.
A separation wall 30 formed from elastic material such as metal is disposed between the first liquid passage and the second liquid passage to isolate the first liquid passage from the second liquid passage. Incidentally, when the mixing between the bubble liquid and the discharge liquid is desired to prevent as much as possible, the liquid in the first liquid passage 14 is isolated from the liquid in the second liquid passage 16 by the separation wall as much as possible; whereas, when the bubble liquid and the discharge liquid maybe mixed to some extent, the separation wall may not have the perfect separation function.
A portion of the separation wall positioned in an upper projection space regarding the heat generating element (referred to as xe2x80x9cdischarge pressure generating areaxe2x80x9d hereinafter; area A and area B of the bubble generating area 11 in FIG. 6) constitutes a movable member 31 having a free end 32 disposed at the discharge opening (i.e., toward a downstream side in the liquid flowing direction) and a fulcrum 33 disposed at the common liquid chamber (15, 17) side. Since the movable member 31 is disposed in a confronting relation to the bubble generating area 11 (B), the movable member 31 is moved (as shown by the arrow) by the bubble in the bubble liquid to be opened toward the discharge opening in the first liquid passage. In this case, since the free end of the movable member is more displaceable than the fulcrum, the free end is displaced in accordance with growth of the bubble, thereby directing the bubble toward the discharge opening efficiently. The separation wall 30 is disposed above the element substrate 1 on which heat generating resistance elements as the heat generating elements 2 and wiring electrodes (not shown) for applying electrical signals to the corresponding heat generating resistance elements are arranged, with the interposition of a space defining the second liquid passages.
The positional relation between the fulcrum 33 and the free end 32 of the movable member 31 and the heat generating element are the same as the former embodiments.
Further, while the structural relation between the liquid supply passage 12 and the heat generating element 2 was explained in the previous embodiment, also in this embodiment, a structural relation between the second liquid passage 16 and the heat generating element 2 is the same as the above-mentioned structural relation.
Next, an operation of the liquid discharging head according to this embodiment will be explained with reference to FIGS. 8A and 8B.
Regarding the operation of the head, as the discharge liquid supplied to the first liquid passage 14 and the bubble liquid supplied to the second liquid passage 16, the same water base ink is used.
When the bubble liquid in the bubble generating area in the second liquid passage is subjected to the heat from the heat generating element 2, as is in the former embodiments, a bubble 40 is formed in the bubble liquid by film-boiling phenomenon as disclosed in U.S. Pat. No. 4,723,129.
In this embodiment, since the bubble pressure cannot escape through three sides (downstream side and both lateral sides) except through the upstream side of the bubble generating area, the pressure caused by the formation of the bubble is concentrated and transmitted toward the movable member 31, so that, as the bubble is growing, the movable member 31 is displaced from a condition shown in FIG. 8A to a condition shown in FIG. 8B toward the first liquid passage. This movement of the movable member causes the second liquid passage 16 to greatly communicate with the first liquid passage 14, with the result that the pressure of the bubble is mainly transmitted to a direction toward the discharge opening in the first liquid passage (i.e., direction A). The liquid is discharged from the discharge opening 18 by such transmission of the pressure and the mechanical displacement of the movable member.
Then, as the bubble is being contracted, the movable member 31 is returned to condition shown in FIG. 8A, and, in the first liquid passage 14, the discharge liquid corresponding to an amount of the discharged liquid is supplied from the upstream side. Also in this embodiment, since the supply of the discharge liquid is effected toward a direction for closing the movable member as is in the former embodiments, the re-fill of the discharge liquid is not prevented by the movable member.
While function and advantage regarding the transmission of the bubble pressure due to the displacement of the movable member, the growing direction of the bubble and the prevention of the backwave in this embodiment are the same as the first embodiment, the two-liquid passage structure of this embodiment further provides the following advantages.
That is to say, according to the arrangement of this embodiment, since the discharge liquid and the bubble liquid are isolated from each other, the discharge liquid can be discharged by the pressure of the bubble formed in the bubble liquid. Thus, even when high-viscous liquid (such as polyethylene glycol) in which a bubble was not adequately formed and provided only poor discharging force is used, by supplying such high-viscous liquid in the first liquid passage and by supplying liquid (mixed liquid having about 1 to 2 cp; and, ethanol: water = 4:6) in which a bubble can easily be formed or liquid having low boiling point in the second liquid passage, the good discharging can be achieved.
Further, by selecting liquid in which deposit due to heat is not accumulated on the surface of the heat generating element as the bubble liquid, the formation of the bubble can be stabilized and good discharging can be achieved.
In addition, since the head according to this embodiment provides the advantages same as the former embodiments, the liquid such as high-viscous liquid can be discharged with high discharging efficiency and high discharging force.
Further, even when liquid having poor resistance to heat is used, by supplying such liquid in the first liquid passage as discharge liquid and by supplying liquid having good resistance to heat and facilitating the formation of the bubble in the second liquid passage, the liquid can be discharged with high discharging efficiency and high discharging force and without thermal damage of the liquid.
While the liquid passage structure of the liquid discharging head performing the characteristic discharging principle of the present invention was explained with regard to one-liquid passage type and two-liquid passage type, now, an assembled structure of the liquid discharging head and a head cartridge comprised of such a liquid discharging head and an ink tank, which can be applied to the above-mentioned embodiments, can be manufactured easily and cheaply and are effective to high density arrangement of nozzles and in which the number of parts can be reduced and the head can easily be elongated will be explained.
Further, it was found that such a structure which can be manufactured easily and cheaply can also be applied to a head having a new liquid discharging principle utilizing a bubble which could not obtained in the conventional techniques.
A first object of the present invention is to provide a liquid discharging head in which the number of parts is small and which can be manufactured easily and cheaply.
A second object of the present invention is to provide a liquid discharging head in which acccumulation of heat in liquid on heat generating element can be reduced greatly while improving liquid discharging efficiency and a discharging force and good liquid discharging can be achieved by reducing a residual bubble on the heat generating element.
A third object of the present invention is to provide a liquid discharging head in which an inertia force of a back-wave can be suppressed or prevented from acting toward a direction opposite to a liquid supplying direction and re-fill frequency is increased by reducing a retard amount of meniscus by a valve function of a movable member, thereby improving a recording speed.
To achieve the above objects, the present invention provides a liquid discharging head comprising a substrate having a plurality of heat generating elements for generating a bubble in liquid and a grooved member having a plurality of grooves constituting a plurality of liquid passages and wherein the liquid passages for respective heat generating elements are formed by joining the grooved member to the substrate and further wherein the grooved member has an opening portion into which the substrate is inserted and the opening portion has the plurality of grooves which constitute the liquid passages for the respective heat generating elements when the substrate is inserted into the opening portion.
Further, the grooved member has discharge openings communicated with the plurality of grooves of the opening portion. A method for manufacturing such a liquid discharging head is characterized by inserting the substrate into the opening portion while widening the opening portion when the substrate is inserted into the opening portion, and securely holding the substrate within the opening portion by a restoring force of the grooved member. In this case, in order to widen the opening portion of the grooved member, heat is applied to the grooved member and tension is applied to the grooved member in directions that the opening portion is widened.
The liquid discharging head having the above-mentioned construction may further include movable members each of which is disposed in a confronting relation to the corresponding heat generating element and has a free end near the corresponding discharge opening and serves to direct pressure of a bubble generated by the corresponding heat generating element toward the corresponding discharge opening by displacing the free end by the bubble pressure, or, may further include such movable members and liquid supply passages for supplying the liquid onto the heat generating elements from an upstream side along surfaces of the movable members near the heat generating elements.
Alternatively, the liquid discharging head having the above-mentioned construction may be designed so that the liquid passages are divided into first liquid passages communicated with the discharge openings and second liquid passages each including a bubble generating area in which a bubble is generated in the liquid by applying heat to the liquid, and there are provided movable members each having a free end near the corresponding discharge opening and each serving to direct pressure of a bubble generated in the corresponding bubble generating area toward the corresponding discharge opening of the first liquid passage by displacing the free end toward the first liquid passage by the bubble pressure.
Alternatively, the liquid discharging head may comprise an element substrate having a plurality of heat generating elements for generating a bubble in liquid, and a grooved member having an opening portion into which the substrate can be inserted and a plurality of grooves for constituting a plurality of liquid passages when the substrate is inserted in the opening portion and wherein the liquid passages are divided into first liquid passages communicated with the discharge openings and second liquid passages within which the respective heat generating elements are disposed and may further comprise a separation wall having movable members each capable of being displaced by pressure of a generated bubble to direct the pressure toward the corresponding discharge opening thereby to discharge the liquid.
The present invention further provides a head cartridge comprising such a liquid discharging head and a liquid container for holding liquid to be supplied to the liquid discharging head.
The present invention also provides a liquid discharging apparatus comprising such a liquid discharging head, and a drive signal supplying means for supplying a drive signal for causing the liquid discharging head to discharge the liquid or a recording medium conveying means for conveying a recording medium for receiving the liquid discharged from the liquid discharging head.
With the arrangement as mentioned above, by providing the opening portion (into which the substrate having the plurality of heat generating elements for generating a bubble can be inserted) in the grooved member having the plurality of grooves for constituting the plurality of liquid passages so that the liquid passages for the respective heat generating elements are formed when the substrate is inserted within the opening portion, since the liquid discharging head can be completed merely by inserting the substrate into the opening portion of the grooved member, the number of parts can be reduced and the head can be assembled easily and cheaply, in comparison with conventional liquid discharging heads. Particularly, since the grooved member has a simple structure only having the plurality of grooves, the grooved member can easily be manufactured and is effective to nozzle arrangement with high density. Further, since any chamber in the grooved member corrected by press-fitting the element substrate into the opening portion of the grooved member, an elongated substrate can be used. In addition, by press-fitting the substrate from a direction perpendicular to the array of grooves, walls defining the grooves are not fallen. Further, since the element substrate is closely contacted with the grooved member by the press-fit, any holding spring is not required unlike to the conventional techniques.
According to the liquid discharging head according to the present invention based on the new discharging principle, since a combined effect between the bubble generated and the movable member displaced by the bubble pressure contributes to discharge the liquid near the discharge opening efficiently, the liquid discharging efficiency can be improved in comparison with the conventional bubble jet discharging methods and heads. For example, in a preferred embodiment of the present invention, the liquid discharging efficiency can be improved by twice or more in comparison with the conventional techniques.
According to the characteristic arrangement of the present invention, even if the head is placed under a low temperature condition and/or a low humidity condition for a long time, the poor discharging can be prevented. If the poor discharging occurs, merely by effecting a recovery treatment such as preliminary discharge and/or suction recovery, the normal condition can easily be restored.
Specifically, even under a long term placement condition wherein many conventional bubble jet heads having 64 discharge openings occur the poor discharging, in the head of the present invention, only about a half or less of the discharge openings cause the poor discharging. Further, when such a head is restored by the preliminary discharge, it was found that, in the conventional head, about 1000 preliminary discharges must be effected for each discharge opening; whereas, in the head of the present invention, the head can be restored merely by about 100 preliminary discharges. This means that the recovery time and the liquid loss during the recovery operation can be reduced and the running cost can be reduced greatly.
Further, according to the arrangement of the present invention in which the re-filling feature is improved, the response in the continuous liquid discharging, stable growth of the bubble and stability of liquid droplets can be improved, thereby permitting high speed recording due to high speed liquid discharging and high quality image recording.
The other advantages of the present invention will be apparent from the detailed explanation of respective embodiments of the present invention.
Incidentally, in the specification and claims, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are referred to regarding the liquid flowing direction from the liquid supply source through the bubble generating area (or movable member) to the discharge opening, or the constructural direction.
Further, the term xe2x80x9cdownstream sidexe2x80x9d regarding the bubble itself mainly means a discharge opening side portion of the bubble directly relating the liquid discharging. More particularly, it means a bubble portion generated at a downstream of a center of the bubble in the liquid flowing direction or the constructural direction or at downstream of a center of the area of the heat generating element.
Further, in the specification and claims, the term xe2x80x9csubstantially closedxe2x80x9d or xe2x80x9csubstantially sealedxe2x80x9d means a condition that, when the bubble is growing, before the movable member is shifted, the bubble cannot escape through a gap (slit) at a downstream side of the movable member.
In addition, the term xe2x80x9cseparation wallxe2x80x9d means a wall (which may include the movable member) disposed to separate the bubble generating area from a area directly communicated with the discharge opening in a broader sense, and means a wall for distinguishing the liquid passage including the bubble generating area from the liquid passage directly communicated with the discharge opening and for preventing the mixing of the liquids in both liquid passages in a narrower sense.